This program project represents an attempt to determine the genetic, imaging, emotional and diagnostic features of frontotemporal 1obar degeneration (FTLD). In project 1 we will positionally clone a locus on chromosome 15 for autosomal dominantly inherited frontotemporal lobar dementia-amyotrophic lateral sclerosis (FTLD-ALS); identify tau-linked sequence changes responsible for susceptibility to sporadic FTLD and progressive supranuclear palsy (PSP); map a susceptibility locus for FTLD that is not due to highly penetrant autosomal dominant loci; and identify and study pre-symptomatic individual and susceptibility mutations. In project 2 we will define the structural, spectroscopic and perfusion changes in FTLD, Alzheimer s disease (AD), PSP and controls. In project 3 we will use methods from behavioral research to evaluate differences and changes in emotional reactivity, regulation of knowledge, and personality in FTLD, AD, and normal controls; evaluate emotional and personality changes associated with tau mutations in families with FTLD; and evaluate behavior in FTLD, AD, and controls by studying dyadic interaction with spouses. In project 4 we will determine with a prospective design the sensitivity and specificity of clinical and quantitative methods for differentiating FTLD and AD; determine the longitudinal changes in basal ganglia and motor neuron function in FTLD compared to AD and healthy controls; and study the cognitive and behavioral features of PSP.